Stub Guard for a Sickle Cutter System

ABSTRACT

In a sickle cutting system, including a plurality of guard fingers in a row across a cutter bar with each guard finger having an upwardly facing ledger surface and a plurality of hold-down members with each hold-down member comprising at least one hold-down finger, the guard fingers and hold down fingers thus forming cooperating overlying pairs between which the blades pass in the cutting action the guard fingers having no portion elevated above the ledger surface thereof in front of the tip of the blade and the guard fingers and blades having lengths from the cutter bar arranged such that a forwardmost tip of the guard finger is forward of the tip of the blade.

This application is a continuation of application Ser. No. 15/681,538filed Aug. 21, 2017.

This invention relates generally to a stub guard for a sickle knifecutter system for harvesting crop with improved cutting action.

BACKGROUND OF THE INVENTION

The present invention relates generally to a crop cutting devicecomprising a frame structure arranged for forward travel over groundhaving a standing crop thereon; a cutter bar secured to the framestructure and extending transversely across a front end of said framestructure; a plurality of knife guards mounted in spaced relation alongsaid cutter bar and projecting forwardly therefrom in transversealignment; each of said guards having an upwardly facing ledger surfacewith opposed side edges thereof arranged to provide first and secondshearing edges; a sickle bar mounted in transversely extending positionand being driven for reciprocating movement relative to said knifeguards; the sickle bar having a plurality of knife blades mountedthereon for movement therewith; each of the knife blades having acutting surface for passing across the ledger surface of the knifeguards and an opposed surface; each of the knife blades having two sidecutting edges which are beveled from the opposed surface to the cuttingsurface to cooperate with said shearing edges of said knife guards; thesickle bar being driven to carry the knife blades back and forth betweenthe knife guards.

It is well known that many sickle knives of this general type include aconventional or pointed guard where the guard is formed as an integralelement which includes a base piece attached to the cutter bar anddefining the ledger surface and a nose piece projecting forwardly fromthe ledger surface in front of the front edge of the blade which isgenerally pointed at a leading end so as to separate the crop to eachside of the guard. This nose piece also stands up in front of the ledgersurface to protect the front edge of the blade and includes a rearwardlyextending shelf over the ledger surface which forms a slot with theledger surface through which the blade passes. Guards of this typeinclude separate hold down members between the guards which applydownward pressure on the cutter bar to press the blades against theledger surface.

Pointed guards generally feature a point with a cut slot that the sickleblades reciprocate in and out of. Various types of hold-down arrangementare used to apply pressure to the sickle to keep its shearing surface inclose contact with the guard ledger as cutting occurs. Usually these arelocated between the guard point or at the rear edge of the sickles. Mostare sheet metal and feature easy adjustment using a hammer or a simplesingle point threaded adjustment. By keeping the hold-downs separatefrom the guards fewer hold-downs than points may be used to reduce thecost and number of adjustments required. Pointed guards have found muchfavor in easier cutting conditions due to the ease of adjustment andsuperior performance.

Another form of guard is known as a stub guard which is formed in twoseparate pieces including a base piece which carries the ledger surfaceand a top piece which extends over the ledger surface. The pieces areseparate and separately adjustable relative to the cutter bar so thatthe top piece can apply pressure onto the blade to press it onto theledger surface. The pieces terminate at a front edge which is justbehind the front edge of the blade so that the front edge of the bladeis presented to the crop.

In tough cutting, stub or no-clog guards have found the most favor. Stubguards use a separate top and bottom guard pieces that spaced slightlymore than one sickle blade thickness apart create a slot for the bladeto operate in. The front edge of the blade protrudes slightly past thefront tip of the two guards. This feature is what originally gavestub-guards their non-clogging self-cleaning action. A major improvementin stub guard technology was made when fully adjustable top hold-downassemblies were introduced. These arrangements allowed the gap to becontrolled much more precisely than previously so that the shearingsurface of the blade was kept in close contact with the guard ledgersurface. This adjustability allows the stub top piece to act as a muchmore effective hold-down than the hold-downs found on regular pointedguard systems.

The pointed guard has an advantage of presenting a point to the incomingcrop so that crop is effectively divided around it. This is especiallyadvantageous when the sickle blade is at or near the end or start ofeach stroke and a front edge of each blade, which is typically a bluntfront edge of a width of the order of 0.5 inch, is hidden partially orentirely within the guard slot. Since the sickle bar velocity is lowestat or near the end or start of each stroke this gives the pointed guarda considerable advantage over the stub guard for most crops.

The guards can be formed as single elements separately mounted on theguard bar or as double or triple elements connected together side byside for common mounting and common adjustment relative to the guardbar. There is no reason why more elements might be included but this isnot typical.

In some cases the arrangement is of the double sickle type where eachsickle bar is essentially half the length of the cutter bar and thecutter bars reciprocate in opposite phase to minimize vibrating mass andvibrations. Usually the sickle bars are timed so that they move inopposite directions so that vibrations induced into the cutter barassembly are minimized.

The sickle knife cutting system has been widely accepted as the mostpower efficient system due to the shearing action. However due to speedrestrictions of generally less than 5 to 8 mph ground speed, othersystems such as rotating flail systems have come into use since thesecan be operated at much higher ground speed of up to 14 mph whilemaintaining a high cutting efficiency. Such rotary systems have howevermuch higher power usage, are limited in width and provide crop handlingdifficulties for forming effective swaths for drying of the crop.

It remains therefore an ongoing and highly desirable objective toconstruct a sickle knife system which can cut standing crop withsufficient cutting efficiency that the ground speed can be significantlyincreased. It is believed that the construction of a sickle cuttingsystem which can operate at ground speeds of greater than 5 to 8 mph andup to 14 mph would enable the advantages of the sickle cutting action totake back the market currently being met by the flail systems.

Cutting crops such as soy beans where the bean pods can be locatedclosely adjacent the ground typically requires low ground speeds ofaround 4 to 5 mph to ensure that the crop is cut and fed into thecombine harvester without too much loss of the pods. Pods can be lost ifthe cutting action causes some or too many of the lowest pods to be leftat the stubble or broken up by the cutting action. It would be highlydesirable to increase cutting speed above the typical range of 4 to 5mph so as to increase this to or above 6 mph.

Cutting crops such as hay or forage crops such as alfalfa or grassestypically allows higher ground speeds of up to 10 mph since the crop ismore resistant to a poor or inefficient cutting action. It would behighly desirable to increase cutting speed above the typical range of upto 10 mph so as to increase this to or above 12 or even 14 mph.

The term “sickle bar” as used herein is intended to refer generally to astructure which supports all of the knife blades at the spaced positionsalong its length and is not intended to be limited to a singlecontinuous element extending along the whole length of the structure.Thus the bar may be formed of different elements at different parts ofthe length and may include pieces below and above the blades.

SUMMARY OF THE INVENTION

According to the invention there is provided a sickle cutting apparatuscomprising:

a plurality of stationary knife guards arranged to be mounted along acutter bar;

a sickle bar mounted in transversely extending position and arranged tobe driven for reciprocating movement relative to said knife guards;

the sickle bar having a plurality of knife blades mounted thereon formovement therewith;

each of the knife blades having a cutting surface for passing across theknife guards;

each of the knife blades having on first and second sides first andsecond side cutting edges converging toward a forward tip of the blade;

each knife guard comprising a base portion arranged to be mounted on thecutter bar and at least one guard finger mounted on the base portion sothat the guard fingers are arranged to be mounted in a row along thecutter bar;

each guard finger having an upwardly facing ledger surface with opposedside edges thereof arranged to provide first and second shearing edgeswhich cooperate with said side cutting edges of said knife blades;

and a plurality of hold-down members arranged to be mounted along thecutter bar;

each hold-down member comprising a base mounting member arranged to beattached to the cutter bar;

each hold-down member comprising at least one hold-down finger thereoncarried on the base mounting member arranged to be at positions spacedlongitudinally of the cutter bar so as to be cantilevered forwardly fromthe cutter bar to a position of a front tip of each hold-down fingerlocated at a spacing in front of the sickle bar above the ledger surfaceof a respective one of the guard fingers;

the guard fingers and hold down fingers thus forming cooperatingoverlying pairs between which the blades pass in the cutting action;

the guard fingers having no portion elevated above the ledger surfacethereof in front of the tip of the blade;

wherein the guard fingers and blades have lengths from the cutter bararranged such that a forwardmost tip of the guard finger is forward ofthe tip of the blade.

Preferably also the guard fingers, blades and hold down fingers havelengths from the cutter bar arranged such that a forwardmost tip of thehold down finger is rearward of the tip of the blade.

Preferably the tip of the guard finger is longer than the tip of theblade by a distance up to 6.0 mm and preferably of the order of 3.0 mm.

Preferably the tip of the hold down finger is shorter than the tip ofthe blade by a distance in the range 1.5 to 10.5 mm and preferably ofthe order of 5.0 mm.

The stubble which is cut by the knife blades and is longer than thenominal cutting height is caused by the distance traveled over theground while crop is in contact with and pushed by elements of theblades and guards as the elements move forward without cuttingoccurring. The elements include a trash bar of the guard and a serratededge of the blade where the crop is pushed forward by engagement into aserration of the serrated edge.

It has been found, as described hereinafter, in relation to theembodiments particularly described, that a significant increase inground speed while maintaining an acceptable level of cutting efficiencyas measured by the average stubble length can be obtained by acombination of one or more of the features where:

a) The distance between the center line of the guards which is generallyequal to the distance between the center line of the blades can be equalto the conventional length of 3.0 inches or may be reduced to a narrowerwidth typically 2.5 or 2.0 inch. This distance may be equal to thestroke length so that a shorter stroke length can allow a significantincrease in reciprocation rate. However the stroke length may be amultiple of the center line distance. Even where the stoke length is notreduced so that the increase in reciprocation rate cannot be achieved,the reduced center line distance has been shown to provide a significantadvantage.

b) the length of the cutting edge of each knife blade as measured from arearmost end of a cutting action to a forwardmost tip of the knife bladeis increased from a conventional length to a length greater than 2.2inches.

c) the width of the ledger surface of each guard at a position thereonaligned with the rear end of the cutting edge of each knife blade isincreased from a conventional length to a length greater than 1.0 inchesor 1.2 or 1.5 inches.

d) the front edge of the blade is formed with a pointed portion wherethe shape of an apex and side edges of the pointed portion are arrangedto shed crop material engaging the point portion as the point portion ismoved forwardly in the crop to one or other side of the point portionfor cutting and to avoid pushing crop forwardly by the point portion.

This combination surprisingly provides a crop cutting efficiency whichis sufficiently high that the ground speed can be increased from theconventional of the order of 5 to 8 mph to 12 to 14 mph. This increaseis significant and significantly alters the ability of the draper headerto harvest forage crops such as alfalfa at greater than 10 mph and up to14 mph and to harvest soy beans at greater than 5 mph and up to 6 or 7mph.

The invention herein can be defined as or relate to the method ofcutting, the header for cutting, the guards and/or the knife blades.Thus each of these components of the invention includes aspects of theinvention which distinguish that component from the prior art as definedhereinafter.

A first improvement can therefore be obtained by providing a knife bladewhich is narrower than conventional system so that typically the widthis equal to approximately 2.0 inches center to center while providing ablade which has a length greater than conventional system so that thelength from the trash bar to the tip is greater than 2.0 inches, greaterthan 2.2 inches or 2.5 inches and typically of the order of or greaterthan 2.75 inches.

This can be further combined with an arrangement in which the width ofthe guard at the trash bar is increased so that the width of each guardat the rear trash bar is equal to the maximum width which can beobtained while leaving a space at the trash bar between the ledgersurfaces of the order of 0.5 inch or the distance necessary to avoidpinching of crop stalks between the ledger surfaces.

Typically each of the knife blades is generally triangular in shape sothat the side edges converge to a front edge at an angle of the order of60 degrees to the direction of reciprocating movement. The blade has abottom cutting surface for passing across the ledger surface of theknife guards and an opposed or upper surface. The two converging sidecutting edges are beveled from the upper surface to the bottom cuttingsurface to cooperate with the shearing edges of said knife guards. Inaddition the beveled side edges are typically serrated with groovesrunning in a direction longitudinal to the reciprocating direction. Inorder to maximize the cutting action, the length of the cutting edge issubstantially the maximum length extending from the trash bar at therear to a position close to the front edge of the blade.

The fore-aft length of a blade has traditionally been in the order of 45mm (1.75 in) from the front of the trash bar, that is the rearmostcutting location or the rear of the cutting action, to the tip of thesection, or 55 mm (2.2 in) from the front edge of the knife back to thetip of the section. Traditionally this dimension is usually similar tothe length of the cutting edge.

In this new arrangement, the fore-aft length of the blade is increasedsubstantially. Thus the length of cutting edge of each sickle blade froma rearmost end of the cutting action at the trash bar, or to the rear ofthe shearing action on the ledger surfaces, to a front edge of the bladein the present invention is greater than 1.75 inches. This can lie inthe range 2.2 to 3.0 inches.

The term “trash bar” as used herein typically is defined by a specifictransverse bar interconnecting to the ledger surfaces of the lowerguards but does not require the provision of a specific bar memberextending across the blades but merely relates to the position of thatcomponent of the system where the crop is halted as it moves rearwardlybetween the guard fingers. Thus at some point the crop is halted so thatit remains in the position where it can be engaged by the side edges ofthe blades and can be cut in the shearing action relative to the sideedges of the ledger surface. This element which halts the crop movementis called herein the “trash bar”.

This also reduces the angle of inward inclination of the cutting edgefrom the typical 30 degrees to an angle less than 20 degrees andtypically of the order of 15 degrees and in the range 15 to 30 degrees.

Thus in one example the blade has a width of 2.0 or 3.0 inches at thebase and a length from the front of the trash bar to the tip of 2.5inches.

It is common practice for sickle sections, of the current type havingbeveled and serrated side edges, to have a front edge in the order of 15mm (0.6 inches) wide. When used with a pointed guard, this is not asmuch of a problem as this edge is sometimes in the shadow of the guard.However, even with pointed guards and certainly when used with stubguards, the wide tip has the potential for running down crop or pushingthe crop forwardly with the forward motion of the cutter bar, thusleaving more long uncut stems greater in length than the nominal minimumvalue above thus significantly increasing the average length with is themeasure herein of cutting efficiency. In present invention the blade isdesigned with a pointed tip, thus eliminating the problem when used withstub guards.

In some crop conditions e.g. forage with a mat of wet leaves near theground, pointed guards will tend to plug due to “mouse nesting” on theguard point. It is therefore important that a cutting system works wellwith stub guards.

The intention is therefore to provide a sickle blade which is as pointedas reasonably practical. A sharp point is difficult to obtain so thattypically the front edge is smoothly curved with a radius of curvatureless than 0.5 inches thus defining a front apex which is sufficientlynarrow to shed crop stalks to each side. That is, each knife blade has afront point portion in front of the cutting edges which has side edgesconverging to front apex where the apex and the side edges are shapedand arranged such that crop material engaging the point portion, as thepoint portion is moved forwardly in the crop, is shed to one or otherside of the point portion for cutting and is not pushed forwardly by thepoint portion. In the present arrangement the front apex is not a pointas this can be damaged but is a curved front edge of a radius ofcurvature less than 0.5 inches and preferably less than 0.25 inches.From this curvature the sides of the pointed portion diverge rearwardlyat an angle approximately equal to or slightly greater than the angle ofthe cutting edges.

In a blade which has a center to center spacing of the order of 2.0inches and a length from apex to trash bar greater than 2.0 inches, theangle of the side edges of the blade is less than 20 degrees and can beas low as 15 degrees.

The angle of the side edges of the front point portion can be be greaterand is typically in the range 30 to 45 degrees and preferably of theorder of 35 degrees.

This curvature at the apex and the angle of divergence from the curvedapex acts to shed the crop to the sides and to avoid trapping andpushing the crop forwardly.

While this is the optimum arrangement, a practical construction may havea straight line across the apex with a transverse width which is muchless than the conventional 0.6 inches and is typically less than 0.25inches.

Thus each knife blade has a front point portion in front of the beveledand serrated side cutting edges which front point portion has side edgesconverging to front apex, where the apex and the side edges of the frontpoint portion are shaped and arranged such that crop material engagingthe front point portion, as the point portion is moved forwardly in thecrop, is shed to one or other side of the front point portion forcutting by the side cutting edges and is not pushed forwardly by thefront point portion.

Preferably the beveled side sedges are serrated in a direction at rightangles to a forward direction.

Preferably the pointed portion has a thickness at the apex equal to thatof the blade.

Preferably the beveled edges are reduced in width at as they approachthe pointed portion leaving a strip of the upper surface between thebeveled edges having thickness equal to that of the blade with sideedges of the strip being parallel to the center line of the blade.

Preferably at this strip the beveled edges become narrower as thebeveled edge approaches the front pointed portion of the blade.

Preferably the beveled edges and the serrations therein terminate at aposition spaced from the apex of the pointed portion such that the frontpointed portion forms an arrow-head shape in front of a forwardmost oneof the serrations with the width of the front pointed portion beingsubstantially equal to the width of the side edges at the forwardmostone of the serrations.

Preferably a center line spacing between each knife blade and the nextis less than 3.0 inches, preferably less than 2.5 inches and morepreferably of the order of or equal to 2.0 inches. Thus the center linespacing can be equal to the conventional value of 3.0 inches.

Preferably a length of each knife blade from the trash bar to aforwardmost tip of the knife blade is greater than 2.0 inches,preferably greater than 2.2 or 2.5 inches and more preferably greaterthan 2.75 inches.

Preferably the front point portion has side edges which are notsharpened.

Preferably the radius of curvature of the front pointed portion at theapex is less than 0.5 inch and more preferably less than 0.25 inch.

The characteristics of the blade defined above, where it is narrowerthan conventional, 2.0 inches as opposed to 3.0 inches, andsignificantly longer, greater than 2.2 inches or 2.5 to 2.75 inches asopposed to 2.2 inches places considerable limitations on the shape andarrangement of the beveled and serrated edges.

In order to form the pointed portion at the front edge in front of thebeveled edges, the beveled edges are reduced in width as they approachthe front edge leaving a strip of the upper surface between the bevelededges with side edges of the strip parallel to a center line of theblade. Thus at this strip the beveled edge becomes narrower and thegrooves in the edge get shorter as the beveled edge approaches the frontapex of the blade. The beveled edges and the serrations thereinterminate at a position spaced from the front apex to define anarrow-head shaped pointed portion in front of the beveled edges whichimparts sufficient strength to the construction to allow the formationof the serrations. The thickness of the blade through the main body ofthe blade excluding the beveled edges is constant so that the pointedportion and the apex have the same thickness as the rest of the mainbody of the blade and the bevel which reduces the thickness does notextend to the apex.

The cutting efficiency and therefore stubble length are also affected bythe width of the cutting edge of the knife guard. Generally, the widthat the rear of the cutting edge on the guard is in the order of 25 mm(1.0 in). In the arrangement of the present invention that width issubstantially increased. Thus the width of each guard at a positionthereon aligned with the rear end of the cutting edge of each blade isgreater than 1.0 inches or 1.2 inches or 1.5 inches. The maximum widthof the guard is slightly less than the center to center spacing of theblades since it is necessary to leave a gap between the guards at theback to prevent pinching the crop and to allow the crop to reach theback for the rearmost cutting action. Thus with a blade center to centerspacing of 2.0 inches the width of the guard is slightly less than thatof the width of the blade or roughly 1.9 inches. Thus with a blade ofthis width, the width of the guards can be as much as 1.9 inches andpreferably lies in the range 1.2 to 1.9 inches. However where the bladeis greater than 2.0 inches in width, the guard can have a width which isbetween 0.5 and 0.1 inches less than the width of the blade.

Thus the arrangement provided herein provides a center line spacingbetween each guard finger and the next which is in some cases less than3.0 inches and more preferably 2.0 inch where a width of each guard atthe rear trash bar is greater than 1.5 inches and preferably 1.75inches.

Thus a width of each guard at the rear trash bar is equal to the maximumwidth which can be obtained while leaving a space at the trash barbetween the ledger surfaces of the order of 0.5 inch or the distancenecessary to avoid pinching of crop stalks between the ledger surfaces.

Preferably the stroke length is equal to the center line spacing betweenthe knife blades.

Preferably, at the position in the stroke where the center line of theknife blades is aligned with the center line of the guard fingers, theside cutting edges of the knife blades substantially directly overliethe side edges of the ledger surface.

Preferably each knife blade has a front point portion in front of theside cutting edges which front point portion has side edges convergingto front apex, where the apex and the side edges of the front pointportion are shaped and arranged such that crop material engaging thefront point portion, as the point portion is moved forwardly in thecrop, is shed to one or other side of the front point portion forcutting by the side cutting edges and is not pushed forwardly by thefront point portion.

Of course ground speed can be increased if the operator has no regardfor cutting effectiveness and the quality of the cut crop. This is ofcourse unacceptable.

One measure of cutting effectiveness is that of the length of stubblewhich remains on the ground. If the cutting blades run at a nominalheight from the ground then they will theoretically cut all crop to anominal length equal to the height of the blade from the ground. Howeverthis does not occur as the sickle knife moves forwardly since not allcrop is cut immediately as it enters the cutting system. As some cuttingis delayed and the crop pushed forwardly by engagement with elements ofthe cutting system to bend over from the normal upstanding position,then some stubble will have a length exceeding the nominal length andthis length difference will increase as the ground speed increases. Thuscutting effectiveness can be measured by detecting and measuring theaverage length difference of stubble which exceeds this nominal length.

An acceptable effectiveness is defined where the average stubble lengthdifference, that is the average length beyond the minimum or nominallength defined by the distance of the blades from the ground, is lessthan 1.0 inches, as measured at a set speed of 10 mph. Thus for examplewhere the nominal height is a typical 1.5 inches, an acceptableeffectiveness is where a measured average length is no greater than 2.5inches.

Of course machines can run at different speeds and there is no intentionherein to limit the speed to a particular value. However as the stubblelength is of course speed dependent, it is necessary, in order toanalyze the system, to set a predetermined value at which the stubblelength is measured.

Of course in a practical situation there may be failures in propercutting action leaving some crop stalks greater than the allowed lengthdifference defined above. However discarding such discernible failuresin the cutting action which are due to cutting errors and are not ameasure of the actual efficiency of the proper cutting, a properefficiency is defined by the average stubble length as set forth above.

Thus the best measure of cutting effectiveness is the stubble lengththat is left after cutting. The requirement however will vary dependingon the crop. For example for a wheat crop, it will not be critical thata short stubble length be maintained, as the heads are generally high onthe plant.

In the case of hay (alfalfa) it will be important that a fairly shortstubble length is maintained so that a significant quantity of crop isnot left in the field. A typical acceptable total average stubble lengthin this case would be in the area of 2.75 inches (that is 1.25 incheslonger than the nominal minimum length). Thus the ground speed cantypically exceed the 10 mph value set above for the above analysis andmay be as high as or higher than 14 mph.

In the case of soybeans, the acceptable average stubble length dependson the general height of the lowest bean pod on the plants. Theacceptable average stubble length thus varies from about 2 to 2.5 inchesor 0.5 to 1.0 inches greater than the nominal value. In this case aspeed of less than 10 mph is likely to be desirable.

The guard fingers, knife blades and the trash bar are arranged so as toprovide a cutting action on the crop in which:

-   -   in a first cutting stroke, each knife blade moves across from        one guard finger to the next in a first direction so as to cut        crop located on said first side of the knife blade between the        first cutting edge of the knife blade and the next guard finger        by the shearing action while leaving uncut crop located on the        second side of the knife blade;    -   and, in a second cutting stroke, each knife blade moves across        from the next guard finger to said one guard finger in a second        direction so as to cut crop located on the second side of the        knife blade between the second cutting edge of the knife blade        and said one guard finger by the shearing action, including said        uncut crop, while leaving uncut crop located on the second side        of the knife blade.

While this crop remains upstanding before it is cut, the stubble lengthremains at the nominal value. However as soon as the crop is pushedforwardly by a non-cutting surface or a cutting surface which is not ina cutting action at that position in the stroke, it begins to bend overand its length when it is cut is increased from the nominal value by thedistance the crop is bent forwardly.

The guard fingers, knife blades and the trash bar are shaped andarranged therefore to provide a percentage cutting inefficiency of lessthan 35%, 30% or 25%, at the above set speed of 10 mph and at a sicklestroke rate set at a value which provides inertia values equal to thoseobtained by a three inch stroke at 750 rpm,

where percentage cutting inefficiency is calculated as follows:

-   -   within a rectangular area defined by the length of the knife        stroke and the ground distance traveled during one knife cycle,        the sum of any areas of crop in which the crop remains uncut        until it reaches an element of the cutting system by which the        crop is pushed forward, without cutting, by contact with the        element as the element moves forward;    -   divided by:    -   the rectangular area defined by the length of the knife stroke        and the ground distance traveled during one knife cycle.

Thus in a first cutting stroke, there is an area of crop located on thesecond side of each knife blade in which the crop is gathered by contactwith the guard fingers and trash bar as the guard fingers and trash barmove forward while the knife blade is cutting on said first side of saidknife blade. Symmetrically in a second cutting stroke, there is an areaof crop located on the first side of each knife blade that is gatheredby contact with the guard fingers and trash bar as the guard fingers andtrash bar move forward while the knife blade is cutting on said secondside of said knife blade.

The elements which can engage and push the crop while not cutting thecrop as the blade moves away from those elements include the trash barand the serrated edge of the blade on the understanding that crop cannotslide along the serrated blade but instead will remain at a particularserration and be pushed forward by the blade at that location until thereturn stroke cuts the crop.

There is in many prior art arrangements an area that is generated by anycrop which is pushed forward by contact with a front edge of the knifeblade. In the present invention the blade is of a shape to shed the cropthus reducing this significant inefficiency.

The definition of inefficiency can also be applied at different groundspeeds wherein the percentage cutting inefficiency can calculated at 6mph and at a sickle stroke rate set at a value which provides inertiavalues equal to those obtained by a three inch stroke at 600 rpm, isless than 30%; or the percentage cutting inefficiency can be calculatedat 10 mph and at a sickle stroke rate set at a value which providesinertia values equal to those obtained by a three inch stroke at 750rpm, is less than 35%; or the percentage cutting inefficiency can becalculated at 14 mph and at a sickle stroke rate set at a value whichprovides inertia values equal to those obtained by a three inch strokeat 900 rpm, is less than 40%.

The reason for identifying the theoretical calculated efficiency atthree different speeds of 6, 10 and 14 mph is that different machinescan be designed and arranged to travel at different speeds.

Thus for example a 40 foot header used as a straight cut header for acombine can have a sickle knife length of 40 feet and can be designed totravel in the range 2 to 8 mph so that using a pre-set speed of 6 mphand a stroke rate of 600 rpm falls reasonably in the range of a machineof this type.

The present invention sets out that, at the pre-set speed and pre-setstroke rate, the shape and arrangement of the cutting system is suchthat it obtains the stated inefficiency. Of course, at different speedsand stroke rates, the same cutting system will have differentinefficiencies, but in order to determine whether a cutting systemprovides the inefficiency of the present invention, pre-set parametersmust be determined to allow the calculation to be carried out.

Thus as another example, at 14 mph the machine concerned can be of thetype for cutting hay or forage crops and will have a header of forexample 20 feet in width with two 10 foot sickle knives.

At 10 mph the machine has intermediate characteristics. The pre-setcharacteristics used therefore are set forth as alternative to determinethe actual theoretical calculated inefficiency of the cutting system ofa machine and the calculation can be carried out at those pre-setcharacteristics selected from the above different examples which bestmatch the range of operation of the machine concerned.

As defined in the figures hereinafter, the sickle stroke rate for a 4.0inch stroke, which provides inertia values equal to those obtained by a3.0 inch stroke at 750 rpm, is 650 rpm and the sickle stroke rate for a2.0 inch stroke, which provides inertia values equal to those obtainedby a 3.0 inch stroke at 750 rpm, is 918 rpm.

The pre-set parameters for the inefficiency calculation are set out intable 23 hereinafter.

In order to achieve the above decrease in cutting inefficiency, thefollowing characteristics are preferably to be selected, although othercharacteristics may when analyzed provide the same level ofinefficiency:

-   -   a center line spacing between each knife blade and the next        which is less than 3.0 inches and preferably of the order of 2.0        inches.    -   a length of each knife blade from the trash bar to a forwardmost        tip of the knife blade which is greater than 2.0 inches and        preferably of the order of 2.75 inches.    -   a width of each guard at the rear trash bar which is greater        than 1.0 inches and preferably, for a guard spacing center to        center of 2.0 inches of the order of 1.75 inches. That is the        width of each guard at the rear trash bar is equal to the        maximum width which can be obtained while leaving a space at the        trash bar between the ledger surfaces of the order of 0.5 inch        or the distance necessary to avoid pinching of crop stalks        between the ledger surfaces.

Preferably the stroke length is equal to the center line spacing betweenthe knife blades.

Preferably at the position in the stroke where the center line of theknife blades is aligned with the center line of the guard fingers, theside cutting edges of the knife blades substantially directly overliethe side edges of the ledger surface.

Preferably each knife blade has a front point portion in front of theside cutting edges which front point portion has side edges convergingto front apex, where the apex and the side edges of the front pointportion are shaped and arranged such that crop material engaging thefront point portion, as the point portion is moved forwardly in thecrop, is shed to one or other side of the front point portion forcutting by the side cutting edges and is not pushed forwardly by thefront point portion.

Preferably the front point portion has side edges which are notsharpened.

While much of the description herein is directed to a narrower cuttingsystem using blades of 2 inch width, the same cutting action andoperation of the blades can be obtained with blades which have a spacingfrom tip to tip of 3 inches.

Preferably each blade with a base portion and only two cutting edges isa separate component from each of the other blades so that the sideedges of each blade lie immediately adjacent the side edges of the nextadjacent blades. However blades can be formed in pairs connected to thesame base

Preferably the blade has only a single cut out opening luingsymmetrically on the center line and converging to an apex directedtoward the apes of the blade. However more than one cu out opening canbe provided with different shapes.

Preferably the cut out opening has a rear edge parallel to a rear edgeof the blade, two side edges substantially parallel at right angles tothe rear edge and two converging edges extending from the side edges toa forward apex.

Preferably the length of each blade from the transverse line definingthe rearmost cutting action to the forwardmost tip of the knife blade isgreater than 2.5 inches. A maximum of less than 2.9 inches is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a part of header showing a portion of thesickle knife according to a first embodiment of the present inventionusing a stub guard.

FIG. 2 is a cross-sectional view along the lines 2-2 of FIG. 1.

FIG. 2A is a side elevational view of a sickle apparatus showing theengagement of the front edge of the knife and the engagement of thetrash bar with the crop which leads to cutting inefficiencies leading tomaximum stubble length increases.

FIG. 3 is top plan view of a knife blade for use in the sickle knife ofFIG. 1.

FIG. 4 is a side elevational view along of the knife blade of FIG. 3.

FIG. 5 is top plan view of one knife blade of FIG. 3 on an enlargedscale showing the angles of the side edges for different length blades.

FIG. 6 is top plan view of a knife blade of the type of FIG. 3 showing adifferent width blade.

FIG. 7 is a top plan view of a part of header showing a blade of asickle knife according to a second embodiment of the present inventionusing a pointed guard.

FIG. 8 is a cross-sectional view along the lines 8-8 of FIG. 7.

FIG. 9 is top plan view of another embodiment of cutting system using a3 inch spacing of the blades and using stub guards.

FIG. 10 is a cross sectional view along the lines 10-10 of FIG. 9.

FIG. 11 is a detail of the cross-sectional view of FIG. 10 showing thetips of the bottom guard finger, blade and hold down finger.

FIG. 12 is top plan view of another embodiment of cutting system using a3 inch spacing of the blades and using pointed guards.

FIG. 13 is a cross sectional view along the lines 13-13 of FIG. 12.

FIG. 14 is a detail 14 of the cross-sectional view of FIG. 13 showingthe shape of the tang portion.

FIG. 15 is a detail 15 of the plan view of FIG. 12 showing the shape ofthe tang portion.

FIG. 16 is a top plan view of blade of the embodiments of FIGS. 9 and12.

DETAILED DESCRIPTION

In FIGS. 1 and 2 is shown a first embodiment of a crop cutting devicegenerally indicated at 10. Only a part of the complete machine is shownsince the remainder of the machine may vary widely depending uponrequirements and since the construction is of course well known to aperson skilled in the art. In this embodiment as shown, there is a framegenerally indicated at 11 which forms only one part of the total framestructure that is the part of the frame that is relevant to the presentinvention.

The cutting device 10 further includes a cutter bar 12 attached to theframe structure 11. Thus the frame structure 11 in the part as showncomprises a guard bar 13 to which is attached a plurality of knifeguards 14. The guard bar 13 is attached to the frame structure whichsupports the guard bar in fixed position across the front edge of theframe for a cutting action of the crop cutting device on the standingcrop.

Each knife guard 14 includes one or more guard fingers 14A so thatguards can be arranged with a single finger, pair of fingers or triples.As shown the guard bar forms a triple guard construction with threefingers where a series of such guards are mounted on the guard bar 13 atspaced positions along the length of the guard bar. In the embodiment asshown, only one of the guards is shown but it will be appreciated thatthere are additional guards as required to provide a crop cutting deviceof a required width.

The knife guards shown in FIGS. 1 and 2 are basically of a conventionalconstruction of a stub guard in that each guard finger 14A includes alower portion 15 and an upper portion 16. These two portions are mountedon the guard bar 13 by a mounting arrangement 17 including bolts 18. Themounting arrangement thus attaches a rear end 19 of the lower portion 15rigidly on the underside of the bar 13 so that the fingers of the guardproject forwardly from the bar to a front nose 20. Similarly the upperportion 16 is mounted on the guard bar 13 by an adjustment plate 21attached onto the same bolts 18. Upper portion 16 has fingers whichextend forwardly to a nose 22.

In the embodiment shown the guards are stub guards so that the noses 20,22 of the upper and lower portions substantially overlie one another andconfine between them the blades 23 of the sickle bar or knife back 24.

Each pair of guards thus includes two guard elements each defined by anupper portion and a lower portion and the guard elements are shown inFIG. 1 at 15 and 16. A front crop guide bar or trash bar 28 is alsoprovided. Between the mounting bar 21 and the front guide bar 28 isprovided a channel 25 within which the sickle bar or knife back 24 ismounted for reciprocating movement.

The trash bar may form a continuous bar member extending along the lowerguard portion 15 in front of the bar 24 to prevent any crop reachingthat area. However the trash bar may be formed by any part of the systemwhich prevents the crop from moving rearwardly beyond the rear end ofthe cutting edges of the blades.

There may be a single sickle bar driven from one end or in some casesthere are two sickle bars driven from opposite ends and meeting in themiddle. The sickle bar or bars are driven by the reciprocating drivemotor (not shown but conventional) such that the bar reciprocates backand forth.

In some cases the bar reciprocates by a distance S1 equal to the spacebetween the nose of one guards 15, 16 and that of the next along theguard bar 13 so that the blades reciprocate from a position with thecenter line of the knife aligned with the center line of the first guardto a position aligned with the next and back to the first. In othercases, the reciprocation stroke may be as shown at S2 a multiple of,typically double, the distance between the guards so that the knifemoves from a first guard finger across a second to a third and back tothe first. This arrangement reduces the available reciprocation rate dueto increased acceleration forces but reduces the number of reversals.

Each sickle bar comprises the support bar member 24 and the plurality ofblades indicated at 23. As shown the blades are formed in pairs mountedon a common base as shown in FIG. 3, but individual blades may beprovided or in some cases the blades may have more than two on the samebase.

Each of the blades forms a generally triangular-shaped member which hasa rear end or base 23A bolted to the bar and converges from the rear endto a front end 23B. Each of the blades has a top surface 23D and abottom surface 23E. Each of the blades has a side edge 23F and a secondside edge 23G. The sides edges are beveled from the top surface down tothe bottom surface 23E so that a sharp edge is formed at the bottomsurface at each of the side edges. The blades are also serrated at eachcutting edge with grooves 23L, 23M extending parallel to the bars 24that is at right angles to a center line 23H.

The top member 16 acts to hold the blades downwardly into engagementwith the top ledger surface 15A of the bottom portion 15. The bottomportion 15 has two side edges of the ledger surface 15A as best shown inFIG. 2 with those side edges 15B and 15C acting as side edges of theledger surface 15A. Thus the cutting action of the blades occurs betweenthe ledger 15A and the bottom surface 23E of the blade as the bladereciprocates from its position at one of the guards to its position atthe next adjacent one of the guards. In this cutting action, therefore,the side edge of the blade moves across the space between the guards andenters onto the ledger surface of the next guard in a cutting actionbetween the bottom surface of the blade and the top surface of the guardwhich are immediately adjacent and generally in contact or at leastclosely adjacent to provide a shearing action on the crop.

In these guards, the upper portion 16 acts merely as a hold down membercontacting the upper surface of each of the blades so as to prevent itfrom moving away from the ledger surface 15A by applying pressure tothat upper surface 23D of the blade and holding the blade in contactwith or closely adjacent the ledger surface 15A of the bottom portionwhere the cutting action occurs. The upper portion 16 therefore as shownin FIG. 1 has side surfaces 16B and 16C of the bottom surface 16A whichis narrower than the ledger surface 15A of the bottom portion 15.

The mounting and adjustment arrangements for the bottom portion 15 andthe upper portion 16 can vary in accordance with a number of differentdesigns readily available to a person skilled in the art. It suffice tosay that the hold down portion 16 is adjustable so that the gap betweenthe bottom surface of the hold down portion and the ledger surface ofthe bottom portion 15 can be adjusted to allow the sliding action of theblades while holding the blades in the required position.

The disclosures of the following documents of the present Applicants areincorporated herein by reference or may be referred to for details ofthe construction not provided herein. These show various conventionaldetails of the sickle knife system which can be used in the arrangementherein but are not described as they are known to persons skilled in theart.

U.S. Pat. No. 7,328,565 (Snider) issued Feb. 12, 2008;

U.S. Pat. No. 4,894,979 (Lohrentz) issued Jan. 23, 1990

U.S. Pat. No. 4,909,026 (Molzahn) issued Mar. 20, 1990.

U.S. Pat. No. 6,962,040 (Talbot) issued Nov. 8, 2005.

U.S. application Ser. No. 13/680,557 filed Nov. 19, 2012 based on aProvisional application 61/577,427 filed Dec. 19, 2011 (Talbot) relatingto an adjustable hold down.

In FIG. 1, a drive for knife bar 24 is indicated schematically at 24A.This can comprise any suitable drive system known to persons skilled inthis art of a type which can generate a stroke S1 of 2 inches at a driverate of typically 918 rpm. The system can also be arranged in analternative embodiment to drive the stroke S2 of 4 inches in which casethe reciprocation rate may be lower. The drive system 24A includes aninput from a ground speed indicator 24B which allows automatic adjustingof the stroke rate of the drive system 24A in dependence on groundspeed. As the system herein provides a cutting efficiency which ishigher than that of previous designs and suitable for cutting at speedsas much as 14 mph, it is possible when running at lower ground speedssuch as less than 10 mph to reduce the drive rate of the knife since themaximum cutting effect is not required at those lower ground speeds.Thus the system can be arranged to automatically control the knife speedto a lower fixed value when the ground speed is less than apredetermined set value or to provide a proportional control of thedrive speed.

The knife blade 23 is narrower than conventional system so thattypically the width W is equal to the stroke length which isapproximately 2.0 inches center C to center C while providing a bladewhich has a length L greater than conventional system so that the lengthfrom the trash bar 28 to the tip 23K is greater than 2.0 inches andtypically of the order of or greater than 2.75 inches.

This can be further combined with an arrangement in which the width W1of the guard ledger surface at the trash bar 28 is increased so that thewidth W1 of each guard at the rear trash bar is equal to the maximumwidth which can be obtained while leaving a space S at the trash barbetween the ledger surfaces of the order of 0.5 inch or the distancenecessary to avoid pinching of crop stalks between the ledger surfaces.

Typically each of the knife blades is generally triangular in shape withstraight side edges 23F, 23G. However other shapes of the side edges23F, 23G in plan such as convex or concave can be used. Thus the sideedges 23F, 23G converge to the front apex 23K at an angle of the orderof 60 degrees to the direction of reciprocating movement. The twoconverging side cutting edges 23F, 23G are beveled from the uppersurface 23D to the bottom cutting surface 23E to cooperate with theshearing edges of the knife guards. In addition the beveled side edgesare serrated with grooves 23L, 23M running in a direction longitudinalto the reciprocating direction. In order to maximize the cutting action,the length of the cutting edge is substantially the maximum lengthextending from the trash bar 28 at the rear to a position close to thefront apex 23K of the blade.

In this new arrangement, the conventional fore-aft length of the bladeis increased substantially. Thus the length of cutting edge of eachsickle blade from a rearmost end of the cutting action at the trash bar28, or to the rear of the shearing action on the ledger surfaces 15A, tothe front apex 23K of the blade in the present invention is greater than1.75 inches. This can lie in the range 2.2 to 3.0 inches.

The cutting efficiency and therefore stubble length are also affected bythe width of the cutting edge of the knife guard. In the arrangement ofthe present invention that width is substantially increased. Thus thewidth W1 of each guard at the trash bar 28 is greater than 1.0 inches.The maximum width of the guard is slightly less than the center tocenter spacing of the blades since it is necessary to leave the gap Sbetween the guards at the back to prevent pinching the crop and to allowthe crop to reach the back for the rearmost cutting action. Thus with ablade center to center spacing of 2.0 inches the width W1 of the guardis slightly less than that of the width of the blade or roughly 1.9inches. Thus with a blade of this width, the width of the guards can beas much as 1.9 inches and preferably lies in the range 1.2 to 1.9inches. However where the blade is greater than 2.0 inches in width, theguard has a width which is between 0.5 and 0.1 inches less than thewidth of the blade. At the position in the stroke shown in FIG. 1 wherethe center line C of the knife blades is aligned with the center line Clof the guard fingers, the side cutting edges of the knife blades 23F,23G substantially directly overlie the side edges 15B, 15C of the ledgersurface 15A.

Each knife blade has a front point portion 23X in front of the sidecutting edges 23F, 23G which front point portion has side edges 23N, 23Pconverging to the front apex 23K, where the apex and the side edges ofthe front point portion 23X are shaped and arranged such that cropmaterial engaging the front point portion, as the point portion is movedforwardly in the crop, is shed to one or other side of the front pointportion for cutting by the side cutting edges and is not pushedforwardly by the front point portion 23X.

As shown in FIGS. 3, 4 and 5, the arrow head shaped front point portion23X has side edges 23N, 23P which are not sharpened. The angle of thebevel of the sides 23F and 23G may extend partly into the side edges 23Nand 23P but the side edges 23N and 23P are not beveled to the bottomsurface 23E so that they are not sharp. Also the last serration 23Y ofthe bevel edges 23F and 23G is located at the bottom of the portion 23Xso that the side edges 23N and 23P are not serrated. The pointed portion23X has a thickness at the apex 23K equal to that of the blade so thatas shown in FIG. 4B, the thickness along the center line remainsconstant right up to the apex 23K. The arrangement is designed so thatthe front portion 23X is as thick as possible over its full extentconsistent with the requirement to machine the blade to form the beveledand serrated edges 23F, 23G. Thus the beveled side edges 23N and 23P arereduced in width in plan view at as they approach the pointed portion23X leaving a strip 23R of the upper surface between the beveled edgeshaving thickness equal to that of the blade with side edges 23Q of thestrip being parallel to the center line 23H of the blade. Thus, at thisstrip 23R, the beveled side edges 23N and 23P become narrower as thebeveled side edges 23N and 23P approach the front pointed portion 23X ofthe blade.

The beveled side edges 23N and 23P and the serrations 23L thereinterminate at the position 23Y spaced from the apex 23K of the pointedportion 23X such that the front pointed portion 23X forms an arrow-headshape in front of a forwardmost one 23Y of the serrations with the widthof the front pointed portion 23X being substantially equal to the widthof the side edges 23N and 23P at the forwardmost one 23Y of theserrations.

As shown in FIGS. 3 and 4, a center line spacing CLS between each knifeblade and the next is less than the conventional value of 3.0 inches andpreferably of the order of or equal to 2.0 inches. It will beappreciated that a measurement of center to center spacing which isequal to an integral number of inches is preferred for engineeringreasons but in theory it is not essential to have an integral number andin some cases the spacing can be in millimeters. In practice, a spacingin the range 2.5 to 1.5 inches is suitable. In FIG. 6 (not to scale) awider spacing of 2.5 inches is shown. In FIG. 5 the angles of differentlengths of blade are shown where a blade having a length of at least 2.5inches from the trash bar is shown having an angle A2 of the side edgesand a shorter blade having a length of the order of 2.0 inches from therash bar has angles A3. In each case the angles of the side edges 23Nand 23P is slightly greater than that of the cutting edges.

As shown in FIGS. 3 and 4, a length L along the center line 23H of eachknife blade from the trash bar that is the rearmost end 23T of thecutting edge 23F to the forwardmost tip 23K of the knife blade issubstantially equal to or greater than 2.75 inches. Improvement incutting efficiency is obtained by increasing the length of the blade sothat the selection of a value of at least 2.75 inches is preferred whichprovides the improved cutting action while avoiding a blade which has alength greater than can be manufactured to remain stiff and straight inthe cutting action without danger of bending. Improvement can beobtained at any value greater than conventional blades so that any valuegreater than 2.0 inches is within the invention herein. A length greaterthan 2.5 inches will provide a significant improvement.

In order to provide shedding of crop at the apex, the radius ofcurvature of the front pointed portion at the apex is less than 0.5 inchand preferably less than 0.25 inches. However a blunt front edge ispossible provided it is sufficiently narrow and a value of less than0.25 inch or more preferably less than 0.125 inch is possible. The abovegeometry provides a construction in which the side edges of the bladeare arranged relative to a center line of the blade at an angle lessthan 30 degrees and preferably less than 25 degrees.

Similarly the side edges of the front portion, which are typically butnot necessarily at the same angle as the side edges of the blade, arearranged relative to a center line of the blade at an angle less than 30degrees and preferably less than 25 degrees. In practice this angle ispreferably of the order of 20 degrees.

Thus the preferred construction provides a center line spacing betweeneach knife blade and the next is of the order of or equal to 2.0 inches,the radius of curvature of the front pointed portion at the apex is lessthan 0.25 inch and the side edges of the front portion are arrangedrelative to a center line of the blade at an angle of the order of 20degrees.

As shown in FIG. 1, the width between the centers of the guards isindicated at D. This can be the same as the length of the cutting strokeso that the blades move from a position aligned with the center line ofone guard finger to that of the next. However in some embodiments thestroke may be a multiple of the distance D, typically twice, so that theblades move from the first guard finger to the third crossing thesecond. The reversal of the reciprocating action at the guard centerline ensure that the blades are stationary and therefore carrying out nocutting when they are overlying the guard and not at an intermediatelocation. The increase of the stroke length to a multiple of the fingerreduces the number of times the blades are stationary but requires areduced stroke rate due to the increased forces on the drives system.

This distance D is less than 3.0 inches and is more preferably of theorder of 2.0 inches. Typically the stroke can lie in the range 1.5 to2.5 inches since this provides a stroke length which allows an increasein the cutting reciprocation rate of the sickle bar by a percentage ofthe order of 22%. This allows a typical rate of 600 cycles per minute,suitable for a 40 ft sickle bar, to be increased a rate greater than750. For shorter bars this rate can be greater than 900. The length ofthe stroke and the rate are determined by the selected geometry of thedrive system.

Typically each of the knife blades 23, as shown in FIG. 2, is generallytriangular in shape. In the example shown, the blade 23 forms a doubleblade connected by a base 23A. The base has holes 23J for mounting onthe blade drive bar 24. The blade 23 has two side edges 23F, 23G whichconverge at an angle A to the direction of reciprocating movement. Atthe front of the blade is provided a front apex 23K of a front arrowhead shaped portion 23X.

The blade has a bottom cutting surface 23E for passing across the ledgersurface 15A of the bottom knife guards 15 and an opposed or uppersurface 23D. The two converging side cutting edges 23F, 23G are beveledfrom the upper surface 23D to the bottom cutting surface 23E tocooperate with the shearing edges of the knife guards. In addition thebeveled side edges 23F, 23G are typically serrated with grooves 23L, 23Mrunning in a direction longitudinal to the reciprocating direction. Inorder to maximize the cutting action, the length of the cutting edge issubstantially the maximum length extending from the trash bar 28 or therear edge 23T at the rear to a position at the front edge or tip 23K ofthe blade.

The fore-aft length of a blade has traditionally been in the order of1.75 inches from the front of the trash bar to the tip of the section,or 2.2 inches from the front edge of the knife back to the tip of thesection.

In this new arrangement, the fore-aft length L of the blade is increasedsubstantially. Thus the length of the cutting edges of each sickle bladeor blade is greater than 2.2 inches. This can be as much as 2.6 inchesand can lie in the range 2.2 to 3.0 inches.

This also reduces the angle A of inward inclination of the cutting edgefrom the typical 30 degrees relative to the center line (an equilateraltriangle) to an angle less than 30 degrees and typically of the order of15 degrees and in the range 15 to 30 degrees.

It is common practice for sickle blades to have the front edge as atransverse straight edge in the order of 0.6 inches wide. The wide tiphas the potential for running down crop, thus leaving long uncut stems.In the present invention the blade is designed with a pointed tip orfront apex 23K, thus eliminating the problem.

The intention is therefore to provide a sickle blade which is as pointedat the front apex 23K as reasonably practical. A sharp point isdifficult to obtain so that typically the front apex 23K is smoothlycurved with a radius of curvature R of a curvature circle C less than0.5 inches thus defining the front apex 23K which is sufficiently narrowto shed crop stalks to each side.

Each knife blade therefore has a front point portion in front of thecutting edges which has side edges 23N, 23P converging to front apexwhere the apex and the side edges are shaped and arranged such that cropmaterial engaging the point portion as the point portion is movedforwardly in the crop is shed to one or other side of the point portionfor cutting and is not pushed forwardly by the point portion.

While this is the optimum arrangement, a practical construction may havea transverse width of a straight line across the apex 23K which is muchless than the conventional 0.7 inches and is typically less than 0.25inches. This narrow front edge is selected to be sufficiently narrow sothat crop is shed to either side and not pushed forwardly as the blademoves forwardly.

The side edges 23N and 23P are inclined outwardly and away from the apexat an angle A1 relative to the center line 23H of the order of 35degrees and certainly less than 45 degrees to the center line 23H.

The characteristics of the blade defined above where it is much narrowerthan conventional and significantly longer places limitations on theshape and arrangement of the beveled and serrated edges 23F, 23G.

Thus the beveled edges 23F, 23G are reduced in width at 23Q as theyapproach the front edge pointed portion 23K at the apex 23X leaving astrip 23R of the upper surface between the beveled edges with parallelside edges of the strip 23R. Thus at this strip 23R the beveled edge23F, 23G becomes narrower and the grooves 23L, 23M in the edge getshorter as the beveled edge approaches the front pointed portion 23X ofthe blade. The beveled edges 23F, 23G and the grooves 23L, 23M thereinterminate at a position spaced from the front apex 23K to define thearrow head shaped portion 23X in front of the beveled edges whichimparts sufficient strength to the construction to allow the formationof the serrations.

The cutting efficiency and therefore stubble length are also affected bythe width of the cutting edge 15B, 15C of the ledger surface 15A of theknife guard 15. Generally, the width W1 between the edges 15B and 15C atthe rear of the cutting edge on the guard in the arrangement of thepresent invention is substantially increased from the conventional widthof the order of 1.0 inches. Thus the width W1 of each guard at aposition thereon aligned with the rear end of the cutting edge of eachblade is greater than 1.0 inches. The maximum width with a blade of 2.0inches in width is slightly less than that of the width of the blade orroughly 1.9 inches. Thus with a blade of this width, the width of theguards can be as much as 1.9 inches and preferably lies in the range 1.2to 1.9 inches. However where the blade is greater than 2.0 inches inwidth, the guard has a width which is between 0.5 and 0.1 inches lessthan the width of the blade. The bottom guard also tapers so that itsedges 15B and 15C lie closely adjacent the edges of the blade when theblade and guard are in the aligned position at the end of a stroke. Thusthe angle of convergence of the edges 15A and 15B matches closely theangle A. This leaves a space S at the rear of the guards 15 at the trashbar 28 to avoid pinching crop at this location. This space S generallyshould be greater than 0.4 inches and typically is of the order of 0.5inches.

Thus the cutting system is carried so that it moves across the groundeither closely in contact with the ground as shown or at a set cuttingheight. In both cases this determines a cutting height or nominalcutting distance from the ground with is the length of any crop stalk ifcut efficiently and directly as it reaches the location between theblade and ledger surface. In FIG. 2, the cutter bar rests on the groundat a skid plate 80 which holds the ledger surface 15A at the height NDfrom the ground. Typically this is of the order of 1.5 inches but thiscan be varied slightly by changing the angle of the cutter bar about atransverse axis by changing the angle of the header.

Turning now to FIGS. 7 and 8, the shape of the pointed guard for use inthe present invention in conjunction with the pointed blade is shown anddescribed in more detail as follows.

The knife guard 30 for use in a sickle cutting apparatus 10 includes theframe structure 11, guard bar 13, sickle bar 24 and knife blades 23 aspreviously described. Each the knife blades 23 has a cutting surface 23Dfor passing across the ledger surface 15A of the knife guards 151. Eachof the knife blades has on first and second sides first and second sidecutting edges as previously described to cooperate with shearing edges152 of the guard guards 151.

The knife guard 151 includes a base portion 154 for mounting on thecutter bar 13, a rear trash bar 28 in front of the base portion 154 andat least one guard finger 153. In this embodiment three fingers 153 arearranged in a row, where the finger or fingers 153 are mounted on thebase portion 154 so that the fingers are arranged in a row along thecutter bar with a space 155 between each finger and the next allowingcrop to enter the space up to a position of engagement with the reartrash bar 28.

The guard fingers have the upwardly facing ledger surface 15A withopposed side edges arranged to provide first and second shearing edges.The guard fingers have a downwardly facing ground engaging surface 156shaped and arranged to provide protection for stone engagement as thefingers slide over the ground. That is each finger has sufficientstrength to avoid breakage when impacting stones and obstacles causingthe cutter bar to rise if the impact is sufficient and extends oversufficient number of guard fingers to provide the lifting action. Thisshape of the ground engaging surface is well known to persons skilled inthe art and includes a longitudinal rib which is generally triangular incross-section on the underside of the upper part containing the ledgersurface. The base of the rib thus forms an apex which runs over theground to prevent upward forces from snapping the guard finger at theledger surface.

An upstanding transverse shoulder 157 is provided at a front edge of theledger surface 15A and extends upwardly to a top surface 158 of thefinger where the shoulder terminates. Thus there is no tang ofconventional shape, that is no portion of the guard extending rearwardlyover the ledger surface 15A from the shoulder 158. Above the ledgesurface therefore the knife blades are free from confinement by aconventional tang as used in a conventional pointed guard or by acooperating upper guard finger of the type used in a stub guard asdescribed above.

A tip portion 159 in front of the ledger surface extends forwardly fromthe shoulder 158 and defines a forwardmost generally pointed tip 160 forengaging crop in front of the ledger surface 15A.

A length L1 of the ledger surface 15A from the trash bar 28 to theshoulder 157 is greater than 2.0 inches or more preferably greater than2.5 inches; and a length L2 of the tip portion 159 from the shoulder tothe tip is less than 1.0 inch or more preferably less than or equal to0.75 inches.

As defined previously, a center line spacing between each knife guardfinger and the next is less than 3.0 inches and preferably of the orderof 2.0 inches.

As defined previously, a width of each guard finger at the rear trashbar is greater than 1.0 inches and more preferably is greater than 1.5inches or equal to the maximum width which can be obtained while leavinga space at the trash bar between the ledger surfaces in the range 0.25to 0.5 inch or the distance necessary to avoid pinching of crop stalksbetween the ledger surfaces.

The side edges of the ledger surface 15A converge from the trash bar 28to the shoulder 15 at an angle A4 greater than 10 degrees and preferablyof the order of 12 degrees to a line LR at right angles to the trash baror parallel to the center line CL. The angle A5 of the side edges at theshoulder increases so that the tip portion is shorter than would be thecase if the angle A4 were continued up to the tip. However overall, itwill be appreciated that a line joining the rear end 161 of the sideedge 151 of the ledger surface 15A and the tip 160 converges at an anglegreater than the 10 degrees of the side edge to a line at right anglesto the trash bar.

As the side edges converge at a relatively rapid angle from the base tothe tip, the ledger surface has a width W3 at the shoulder 157 of lessthan 0.75 inches and preferably of the order of 0.5 inches.

There is also provided a plurality of separate hold down members 162arranged to engage the blades at every third spaced ones of the fingers.This has a base portion 163 mounted on the cutter bar 13 and a fingerportion 164 extending over the ledger surface of one of the fingers 14A.

Generally the cutting speed can be increased as the speed of the sickleis increased. One limitation for the sickle speed is the stress that isinduced in the sickle drive and the knife back from the inertia loadsresulting from the acceleration of the sickle at the start of thestroke. These acceleration loads are proportional to the stroke lengthand to the square of the sickle speed.

Therefore for the same acceleration loads, if the stroke is decreased,the speed can be increased by an amount represented by the followingformula:

stroke2=stroke1×rpm1{circumflex over ( )}2/rpm2{circumflex over ( )}2

or in terms or speed:

rpm2=(stroke1×rpm1{circumflex over ( )}2/stroke2){circumflex over( )}0.5

For example for a typical 35 ft header and a single sickle knife drivenfrom one side, to achieve the same loads, if a sickle with a 3 inchstroke, is run at 750 rpm, a sickle with a 2 inch stroke can be run at918 rpm for the same inertia loads.

This distance of the cutting stroke is less than 3.0 inches and is morepreferably of the order of 2.0 inches. Typically the stroke can lie inthe range 1.5 to 2.5 inches since this provides a stroke length whichallows an increase in the cutting reciprocation rate of the sickle bar.This rate is preferably greater than 900. A range of 900 to 1200 rpm isparticularly suitable depending on the length of the sickle.

Thus, the maximum sickle speed is affected by the length of the sickleassembly. Generally headers vary in width from 15 ft to 45 ft and aregenerally available in single knife drive for widths up to 40 ft.Therefore the length of the sickle can vary in length from 7.5 ft to 40ft.

Where the maximum speed for a 40 ft single knife drive (SK) header witha 3.0 inch stroke might be set at 600 rpm, the maximum speed for 15 ftdouble knife drive (DK) header might be set at 950 rpm.

Therefore in the case of a 2 inch cutting stroke, the cutting speed ofthe new system will be increased by a percentage (22.4%) over thecurrent system. Depending on the length of the sickle, for same inertialoads, the sickle speed can be increased.

It has been found with the current cutting system, that the increasingthe knife speed beyond a speed of about 950 rpm (1900 strokes perminute) produces little improvement in cutting performance. It issuspected that this is due to the blunt face of the traditional knifeblade or sickle section essentially creating a wall that prevents cropfrom entering the cutting area.

Turning now to the cutting efficiency obtained by the above geometry ofcutting system relative to prior art arrangements shown in FIGS. 9 to13, a generic cutting system is shown in FIG. 2A to show how cuttinginefficiency and the associated increase in maximum stubble lengtharises.

Thus in FIG. 2A, the cutting system is carried so that it moves acrossthe ground either closely in contact with the ground as shown or at aset cutting height. In both cases this determines a cutting height ornominal cutting distance ND from the ground with is the length of anycrop stalk if cut efficiently and directly as it reaches the locationbetween the blade and ledger surface. In FIG. 2A, the cutter bar restson the ground at a skid plate 80 which holds the ledger surface 15A atthe height ND from the ground. Typically this is of the order of 1.5inches but this can be varied slightly by changing the angle of thecutter bar about a transverse axis by changing the angle of the header.

Cutting inefficiency arises where stalk S1 engages a blunt front edge23BL of the knife blade 23 so that it is pushed forwardly by the knifeblade rather than reaching the side edges of the knife blade where itcan be cut.

In conventional thinking it is understood that this effect is of littleimportance in that the knife blade is moving rapidly side to side withthe expectation that the sideways movement will immediately cause anysuch crop to be shed to the side away from the movement allowing it tobe quickly cut.

However the analysis of the cutting system shows that, at high groundspeed, the forward movement has much more effect on the crop than thesideways movement so that a band remains in contact with the blunt frontedge L. This crop is then pushed forward forwardly and downwards withoutcutting until the crop is shed from the blade at the location where theblade reverses at the next guard finger, or at some point prior to thatlocation, so that the crop can then enter into the shearing action onthe second side of the blade.

Another analysis shows that, in each cycle of cutting crop, the side ofthe blade which is not cutting will allow some stalks to move to aposition between and the guard as the blade moves away from the guardsufficiently that the blade reaches a position in which the stalksengage the trash bar. Again therefore these stalks are pushed forwardlyand downwards by the trash bar without cutting until the blade comesback in the reverse direction to effect the shearing action of the cropof that second side of the guard.

It is known that sideways movement of the crop also occurs duringcutting. That is each stalk is carried sideways by the moving blade intothe shearing action with the guard finger. This amount of movementvaries depending on the timing of the stalk entering the area to be cutand engaging the blade and the side to side position of the stalk as itenters the area. The amount of sideways movement will of course increasethe length of the stalk as it is cut since the position of the cut is ata height of the stalk greater than the distance ND from the ground. Theanalysis herein does not take into account this sideways movement sincethe maximum stalk length which can be obtained by the sideways movementis always less than the maximum stalk length which is obtained by theabove described forward movement.

However another benefit of the wider guard fingers is that the cropmoves to the side by a shorter distance before encountering the shearingaction at the side edge of the guard.

It will be appreciated therefore that some stalks provide stubble lengthof ND because they are cut without any forward pushing movement and somestalks are pushed forward to a length L2 or L3 where the actual stubblelength is equal to the hypotenuse of the distance of forward movementbefore cutting occurs and distance ND.

As shown as an example in FIG. 12A, the guard fingers 15, knife blades23 and the trash bar 28 are arranged so as to provide a cutting actionon the crop in which in a first cutting stroke, each knife blade 23moves across from one guard finger 151 to the next 152 in a firstdirection 231 so as to cut crop located on said first side of the knifeblade 23 between the first cutting edge of the knife blade and the side15C of the next guard finger 152 by the shearing action while leavinguncut crop located on the second side of the knife blade. In a secondcutting stroke, each knife blade moves across from the next guard finger152 to said one guard finger 151 in a second direction opposite todirection 231 so as to cut crop located on the second side of the knifeblade between the second cutting edge of the knife blade and the guardfinger 151 by the shearing action. The cutting action includes thepreviously uncut crop located on the first side of the blade 23, whileleaving uncut crop located on the second side of the knife blade.

Turning now to FIGS. 9,10 and 11 there is shown a stub guard systemsimilar to that previously described and shown in FIGS. 1 and 2 andincluding many of the features previously defined above. In thisembodiment, however the system is a 3 inch system so that the tip to tipspacing of the blades and guards is 3 inches and the stroke of thesickle knife drive is also 3 inches so that the blades reciprocate backand forth between a first points aligned with one guard to a pointaligned with the next. Thus as shown in the stub guard system of thesefigures there is provided a bottom guard 50, a top hold down 51 and aset of blades 52 carried on the reciprocating sickle bar.

In this embodiment the shape and arrangement of these components issubstantially as previously described except that each guard element hasonly two fingers so that the pair of fingers of the bottom guardunderlie the pair of fingers of the top hold down.

The pair of fingers of the top hold down are individually adjustable soas to change the spacing SP between the finger 51A and the ledgersurface of the guard finger 50A using the construction as shown anddescribed in U.S. Pat. No. 9,622,405 (Talbot) assigned to the presentapplicant and issued Apr. 18, 2017.

As best shown in FIGS. 10 and 11, the guard fingers 50A and blades 52have lengths from the cutter bar arranged such that a forwardmost tip50B of the guard finger 59A is forward of the tip 52B of the blade 52and a forwardmost tip 51B of the hold down finger 51A is rearward of thetip 52B of the blade 52.

Preferably the tip of the guard finger is longer than the tip of theblade by a distance up to 6.0 mm and preferably of the order of 3.0 mm.

Preferably the tip of the hold down finger is shorter than the tip ofthe blade by a distance in the range 1.5 to 10.5 mm and preferably ofthe order of 5.0 mm.

That is the fingers form a conventional stub guard where there is nocomponent of the lower stub guard finger which is above the ledgersurface. However in this arrangement the tip 50B is located just infront of the tip of the blade rather than behind the tip of the blade aswould be conventional. It has been found that this arrangement allowsthe clearing of the blade tip in tough cutting conditions as does anormal stub guard system but in addition the slightly longer fingercooperates with the pointed blade system described in detail hereinwhere there is an additional point portion in front of the conventionalbeveled side cutting edges of the blade. This may improve the cuttingaction and may protect the point against damage while still allowing theclearing action of the crop from the front of the guards and blade whichis obtained using a stub guard system.

Turning now to FIGS. 12 to 15 there is shown a pointed guard systemsimilar to that previously described and shown in FIGS. 7 and 8 above.

In this arrangement however the pointed guard arrangement 60 includes atang portion 62 overlying the ledger surface 61 so that the blade 52passes through a slot 63 defined between the underside 65 of the tangportion and the ledger surface. The tang portion is connected to thetang portion in front of the slot by a pointed portion 64 of the pointedguard which converges to a front tip in front of the forward tip of theblade. The tang portion 62 extends rearwardly over the ledger surfacefrom the point portion 64 to a rear edge 65 of the tang portion. Asshown in FIG. 12, the rear edge 65 is aligned with a trash bar 66 of theguard which extends outwardly to each side of the ledger surface. Asdescribed above therefore the trash bar 66 forms or defines a transverseline across the ledger surface which constitutes the line of therearmost cutting action of the blade on the ledger surface. This line iscoincident with the rear edge of the sharpened cutting edge of theblade.

As shown in FIG. 12, the width of the tang portion at the rear edge 65is equal to the width of the ledger surface of the guard at this pointwhich is greater than 1.2 inches and more preferably of the order of 1.5inches. This wider width of the guard and tang portion than isconventional in systems of this type provides an improved cutting actionwith the blade as described in more detail above. This wider width ofthe tang portion also operates to provide improved control over theblade as it reciprocates through the slot. Even though the blade iscontacted by a hold down finger 68 between the guards, there is atendency for it to rise so that the increased width of the tang portionensures that it is properly guided into the slot as it approaches theslot from one side. Thus a width WT of the tang portion across the guardfinger at the rear end of the tang portion is greater than 1.2 inchesand more preferably 1.5 inches.

As best shown in FIG. 15, the lower surface 69 of the tang portionincludes a first portion 70 extending along the slot from the front ofthe blade to a junction point 72 where the first portion joins a secondportion 71. The lower surface of the tang portion thus includes a firstportion adjacent the tip portion which is generally parallel to theledger surface and a second portion adjacent the rear edge which isinclined at an angle away from the ledger surface. The first portion isplanar and parallel to the plane of the ledger surface. The secondportion is also planar and is inclined upwardly away from the ledgersurface from a transverse line at the junction 72 up to the rear tip 65.This shape of the slot surface of the underside of the tang portionprovides effective control of the blade movement across the ledgersurface while also allowing the guard to be disconnected from themounting bolts and tilted about the line at the junction 72 to lift thetip upwardly and to lower the rear edge downwardly to allow the guard tobe pulled out forwardly with the blade and sickle bar 76 in place. Thisallows the rear of the guard to clear the sickle bar to move forwardlyaway from the cutter bar 77.

In one arrangement, the second portion of the tang portion at theinclined angle is obtained by bending the tang upwardly at the junctionline 72 relative to the first portion. This bending action occurs at thearrow 79 and results in a situation where both the upper and lowersurfaces are inclined cause by the bending of the material forming thetang portion.

As an alternative, the second portion of the tang portion tapers indepth TD from the lower surface to an upper surface thereof toward therear edge 65 thereof.

As shown in FIG. 13, a length along the tang portion of second portion72 from the rear edge 65 to the first portion at the junction 72 isshorter that a length of the first portion 70 to the tip portion 64.Thus the main body of the slot is parallel to properly guide the bladeand only a relatively short part of the slot is inclined upwardly.

Turning now to FIG. 16, there is shown a blade 52 for use with thesystems of FIGS. 9 and 12. It will be noted that the blade member whichhas a base portion 80 to attach to the sickle bar 76 forms a singleblade and not a double blade arrangement as shown and describedpreviously herein. Each blade is therefore a separate component fromeach of the other blades with two side edges 81, 82 so that the sideedges of each blade lie immediately adjacent the side edges of the nextadjacent blades when fastened to the sickle bar 76.

The base portion 80 has two countersunk holes 83 connected to slots 84which communicate with the rear edge 85 of the mounting portion. Thisallows the blade to be pulled from the sickle bar 76 simply by looseningmounting bolts 86 (FIG. 13) sufficiently to allow the bolts to slidealong the slots. This arrangement is described in more detail in U.S.Pat. No. 8,893,462 (Talbot) issued Nov. 25, 2014 and assigned to thepresent applicant, the disclosure of which is incorporated herein byreference.

Each knife blade has a front point portion 87 in front of the sidecutting edges 88, 89 which front point portion has side edges 90, 91converging to a front apex 92. This construction is substantially aspreviously described with the exception that the wider blade of 3 inchesrather than the previous shown 2 inches provides a shorter and lesspronounced point portion. However the point portion has the sameconstruction relative to the beveled and serrated side edges aspreviously described.

Also as shown in FIG. 16, a length LB1 of each knife blade from thetransverse line TL to the forwardmost tip 92 of the knife blade isgreater than 2.2 inches and preferably greater than 2.5 inches. Asdescribed before, the transverse line TL coincides with or is defined bythe front of the trash bar and the rear of the beveled edges which formthe rearmost line of cutting action of the blade on the guard ledgersurface.

Also as shown in FIG. 16, each blade has a cut out opening 93 throughthe blade extending from a rear edge 99 of the opening adjacent to butspaced from a rear edge 85 of the blade toward the tip of the blade. Thecut out opening 93 has a rear edge 99 parallel to a rear edge 85 of theblade, two side edges 94, 95 substantially parallel at right angles tothe rear edge 99 and two converging edges 96, 97 extending from the sideedges to a forward apex 98. This shape takes out an amount of thematerial of the blade which ensures that the blade has approximately thesame weight as a conventional 3 inch blade of a conventional lengthrather than the increased length herein. The shape and location of thecut out opening ensures that the material is removed withoutcompromising the strength of the blade to meet its required loadingsform the cutting action. The cut out opening does not interfere with thesliding action of the hold down fingers over the upper surface.

1. A sickle cutting apparatus comprising: a plurality of stationaryknife guards arranged to be mounted along a cutter bar; a sickle barmounted in transversely extending position and arranged to be driven forreciprocating movement relative to said knife guards; the sickle barhaving a plurality of knife blades mounted thereon for movementtherewith; each of the knife blades having a cutting surface for passingacross the knife guards and an opposed surface; each of the knife bladeshaving on first and second sides first and second side cutting edgesconverging toward a forward tip of the blade; each knife guardcomprising a base portion arranged to be mounted on the cutter bar andat least one guard finger mounted on the base portion so that the guardfingers are arranged to be mounted in a row along the cutter bar; eachguard finger having an upwardly facing ledger surface with opposed sideedges thereof arranged to provide first and second shearing edges whichcooperate with said side cutting edges of said knife blades; and aplurality of hold-down members arranged to be mounted along the cutterbar; each hold-down member comprising a base mounting member arranged tobe attached to the cutter bar; each hold-down member comprising at leastone hold-down finger thereon carried on the base mounting memberarranged to be at positions spaced longitudinally of the cutter bar soas to be cantilevered forwardly from the cutter bar to a position of afront tip of each hold-down finger located at a spacing in front of thesickle bar above the ledger surface of a respective one of the guardfingers; the guard fingers and hold down fingers thus formingcooperating overlying pairs between which the blades pass in the cuttingaction with each guard finger having a respective hold down fingeraligned therewith; the guard fingers having no portion elevated abovethe ledger surface thereof in front of the tip of the blade; wherein theguard fingers and blades have lengths from the cutter bar arranged suchthat a forwardmost tip of the guard finger is forward of the tip of theblade.
 2. The sickle cutting apparatus according to claim 1 wherein eachblade is a separate component from each of the other blades with twoside edges so that the side edges of each blade lie immediately adjacentthe side edges of the next adjacent blades.
 3. The sickle cuttingapparatus according to claim 1 wherein a width of each guard at atransverse rearmost cutting line at which a cutting action occurs isgreater than 1.2 inches.
 4. The sickle cutting apparatus according toclaim 1 wherein a width of each guard at a transverse rearmost cuttingline at which a cutting action occurs is greater than 1.5 inches.
 5. Thesickle cutting apparatus according to claim 4 wherein the transverseline is defined by a trash bar attached to the guard finger andextending outwardly to the sides thereof.
 6. The sickle cuttingapparatus according to claim 1 wherein a stroke length of thereciprocating movement is equal to the center line spacing between theknife blades.
 7. The sickle cutting apparatus according to claim 1wherein each of the hold down fingers is adjustable by a screw to changea spacing thereof from the ledger surface of the guard finger.
 8. Thesickle cutting apparatus according to claim 1 wherein the tip of theguard finger is longer than the tip of the blade by a distance up to 6.0mm and preferably of the order of 3.0 mm.
 9. A sickle cutting apparatuscomprising: a plurality of stationary knife guards arranged to bemounted along a cutter bar; a sickle bar mounted in transverselyextending position and arranged to be driven for reciprocating movementrelative to said knife guards; the sickle bar having a plurality ofknife blades mounted thereon for movement therewith; each of the knifeblades having a cutting surface for passing across the knife guards andan opposed surface; each of the knife blades having on first and secondsides first and second side cutting edges converging toward a forwardtip of the blade; each knife guard comprising a base portion arranged tobe mounted on the cutter bar and at least one guard finger mounted onthe base portion so that the guard fingers are arranged to be mounted ina row along the cutter bar; each guard finger having an upwardly facingledger surface with opposed side edges thereof arranged to provide firstand second shearing edges which cooperate with said side cutting edgesof said knife blades; and a plurality of hold-down members arranged tobe mounted along the cutter bar; each hold-down member comprising a basemounting member arranged to be attached to the cutter bar; eachhold-down member comprising at least one hold-down finger thereoncarried on the base mounting member arranged to be at positions spacedlongitudinally of the cutter bar so as to be cantilevered forwardly fromthe cutter bar to a position of a front tip of each hold-down fingerlocated at a spacing in front of the sickle bar above the ledger surfaceof a respective one of the guard fingers; the guard fingers and holddown fingers thus forming cooperating overlying pairs between which theblades pass in the cutting action with each guard finger having arespective hold down finger aligned therewith; the guard fingers havingno portion elevated above the ledger surface thereof in front of the tipof the blade; wherein the guard fingers and blades have lengths from thecutter bar arranged such that a forwardmost tip of the guard finger isforward of the tip of the blade; and wherein the guard fingers, bladesand hold down fingers have lengths from the cutter bar arranged suchthat a forwardmost tip of the hold down finger is rearward of the tip ofthe blade.
 10. The sickle cutting apparatus according to claim 9 whereineach blade is a separate component from each of the other blades withtwo side edges so that the side edges of each blade lie immediatelyadjacent the side edges of the next adjacent blades.
 11. The sicklecutting apparatus according to claim 9 wherein a width of each guard ata transverse rearmost cutting line at which a cutting action occurs isgreater than 1.2 inches.
 12. The sickle cutting apparatus according toclaim 9 wherein a width of each guard at a transverse rearmost cuttingline at which a cutting action occurs is greater than 1.5 inches. 13.The sickle cutting apparatus according to claim 12 wherein thetransverse line is defined by a trash bar attached to the guard fingerand extending outwardly to the sides thereof.
 14. The sickle cuttingapparatus according to claim 9 wherein a stroke length of thereciprocating movement is equal to the center line spacing between theknife blades.
 15. The sickle cutting apparatus according to claim 9wherein each of the hold down fingers is adjustable by a screw to changea spacing thereof from the ledger surface of the guard finger.
 16. Thesickle cutting apparatus according to claim 9 wherein the tip of theguard finger is longer than the tip of the blade by a distance up to 6.0mm and preferably of the order of 3.0 mm.
 17. The sickle cuttingapparatus according to claim 9 wherein the tip of the hold down fingeris shorter than the tip of the blade by a distance in the range 1.5 to10.5 mm and preferably of the order of 5.0 mm.
 18. A sickle cuttingapparatus comprising: a plurality of stationary knife guards arranged tobe mounted along a cutter bar; a sickle bar mounted in transverselyextending position and arranged to be driven for reciprocating movementrelative to said knife guards; the sickle bar having a plurality ofknife blades mounted thereon for movement therewith; each of the knifeblades having a cutting surface for passing across the knife guards andan opposed surface; each of the knife blades having on first and secondsides first and second side cutting edges converging toward a forwardtip of the blade; each knife guard comprising a base portion arranged tobe mounted on the cutter bar and at least one guard finger mounted onthe base portion so that the guard fingers are arranged to be mounted ina row along the cutter bar; each guard finger having an upwardly facingledger surface with opposed side edges thereof arranged to provide firstand second shearing edges which cooperate with said side cutting edgesof said knife blades; and a plurality of hold-down members arranged tobe mounted along the cutter bar; each hold-down member comprising a basemounting member arranged to be attached to the cutter bar; eachhold-down member comprising at least one hold-down finger thereoncarried on the base mounting member arranged to be at positions spacedlongitudinally of the cutter bar so as to be cantilevered forwardly fromthe cutter bar to a position of a front tip of each hold-down fingerlocated at a spacing in front of the sickle bar above the ledger surfaceof a respective one of the guard fingers; the guard fingers and holddown fingers thus forming cooperating overlying pairs between which theblades pass in the cutting action with each guard finger having arespective hold down finger aligned therewith; the guard fingers havingno portion elevated above the ledger surface thereof in front of the tipof the blade; wherein the guard fingers and blades have lengths from thecutter bar arranged such that a forwardmost tip of the guard finger isforward of the tip of the blade; and wherein the guard fingers, bladesand hold down fingers have lengths from the cutter bar arranged suchthat a forwardmost tip of the hold down finger is rearward of the tip ofthe blade by a distance less than 10.5 mm.
 19. The sickle cuttingapparatus according to claim 18 wherein the tip of the guard finger islonger than the tip of the blade by a distance up to 6.0 mm.
 20. Thesickle cutting apparatus according to claim 18 wherein the tip of thehold down finger is shorter than the tip of the blade by a distance inthe range 1.5 to 10.5 mm.